Generally, spinning reels use a drag mechanism to prevent a cut at the fishing line which is subjected to a greater load by a hooked fish when the rotary frame is rotated to wind up the line to the spool.
The drag mechanism is interposed between the spool, which is supported rotatably to a spool shaft which in turn is supported not-rotatably to the reel body, and the spool shaft, or between the spool shaft fixing the spool and supported rotatably to the reel body and the reel body, so that a drag thumb nut is operated to apply a desired rotational resistance to the spool.
The rotational resistance from the drag mechanism is adjustable by the drag thumb nut to meet durability of the line, but may overcome durability of the line by mistake or by choice of an angler.
There is a spinning reel provided with a lock mechanism besides the drag mechanism so that the spool is fixed not-rotatably with respect to the reel body.
Hence, in a case where a hooked fish abruptly pulls the line, the line may abruptly be subjected to an excessive load overcoming the durability of the line to lead to a cut thereof.